This invention relates to the processing of a continuous web, and more particularly a laminated web which may be of paper or the like. While the present invention may have many applications, it will be described primarily in the manufacture of labels.
In the manufacture of labels, a laminated web, having an upper laminae overlying a substrate, is fed from an unwind roll to the processing machine. The web is such that the laminae is adhered to the substrate by a suitable adhesive, but is easily stripped or peeled from the substrate without damage to either layer. The compositions of the layers are such that nearly all the adhesive remains with the laminae so that a label can be peeled off the substrate and then placed on the object to which it is to be applied such as a container or the like.
The processing machine into which the laminated web is fed, may have several stations which perform various operations on the web as the web travels therethrough. For example, there may be one or more printing stations, cross-perforating, line hole punching, die-cutting, and matrix stripping. It is the matrix stripping operation to which this invention relates.
In a die-cutting station, the upper laminae of the web is die-cut by a rotating die and/or reciprocating dies which penetrates the laminae but not the substrate. This leaves a die-cut pattern defining the shape of the labels, and a waste matrix. At the stripping station the matrix is removed or separated from the web leaving only the substrate and the label portions which may then be further processed onto a rewind roll, by folding, by sheeting, or the like. It is readily appreciated that productivity is directly related to machine speed, and that the machines can be operated at a speed only as fast as the operation station with the least capability. Thus, if one operating station cannot exceed a certain speed, the entire machine will have to be run at that speed even though other operating stations will operate faster. One of the weak links as far as operating speed is concerned has been the stripping station, and this is particularly so where the waste matrix is relatively weak.
The configuration and strength of the waste matrix depends on the die pattern which, because of some job requirements leaves a relatively weak matrix that breaks quite easily or tends to "ride" to the center of the rewind roll. For example, if the matrix includes vertical strands of substantial width, its strength will be sufficient to allow relatively high speed operation, but if there are very few longitudinal strands and they are quite thin, the matrix will easily break and the speed of the machine will have to be reduced substantially to prevent such breakage. Also, if there are only two outside longitudinal strands with no longitudinal strands therebetween, these strands tend to move toward each other causing the rewind matrix roll to bulge at the center. Thus, it is a primary purpose of the present invention to provide a method and apparatus for stripping the matrix from the web at speeds substantially greater than with the conventional method with a corresponding increase in productivity, and where the tendency for the rewind matrix roll to bulge is greatly reduced if not eliminated.
Heretofore, the matrix was stripped from the substrate by passing the matrix over a stripper bar oriented parallel to the plane of the web and normal to the direction of web travel. This meant that the matrix was separated along an axis in the plane of the web which was normal to the direction of web travel. In accordance with the method and apparatus of the present invention, the matrix is separated such that one of its side edges is stripped or peeled from the substrate upstream of its other side edge. This means that the matrix is separated and skewed by turning it away from the substrate along a skewed axis, i.e., an axis other than normal to the direction of web travel. The "skewing angle", which is the angle between the axis in the plane of the web normal to the direction of web travel and the axis in the plane of the web along which the matrix separates, is adjustable so that the optimum skewing angle can be selected for each job, for it has been found that the optimum skewing angle will vary from job to job depending on the matrix configuration.
It is an important aspect of the invention that the skewing angle can be quickly, easily and conveniently selected for optimum conditions. The apparatus of the invention includes a stripper bar and a matrix rewind control assembly, each of which is independently pivotally adjustable for accurate control of the skewed matrix.
It has been found that with the present invention the speeds of operation are substantially increased over the conventional method. The effects of laminae strength, die configuration, and release characteristics are greatly reduced. The result is substantially increased productivity due to increased speed and less downtime from web breakage and other problems. It also makes it possible to operate with a weaker matrix with corresponding savings in web material and more efficient use of machinery, such as dies and the like. Moreover, the skewing tends to hold the longitudinal matrix strands separated for uniform rewinding of the matrix.
These and other objects and advantages of the method and apparatus of the invention are shown by the drawings and detailed description to follow.